Nonlinear Regression with R by Christian Ritz: Used

Regression Modelling with Actuarial and Financial Applications, Edward W. Frees

Wiley Series in Probability and Statistics Ser.: Nonlinear Regression...

ROBUST NONLINEAR REGRESSION: WITH APPLICATIONS USING R BY Gebrenegus Ghilagaber

Nonlinear Regression with R - Paperback, by Ritz Christian; Streibig - Very Good

Modern Methods for Robust Regression

Applied Linear Regression, 2nd ed. Sanford Weisberg HC/DJ

Robust Nonlinear Regression: with Applications using R by Hossein Riazoshams